This invention relates to a two-stroke internal combustion engine comprising cylinder liners which are inserted into the engine housing and each are provided with a chamber containing the cooling water, and with piston-controlled intake and exhaust ports positioned in a thickened sector of their walls. Each cooling water chamber being bounded on the outside by a thin-walled cooling jacket which in the area of the thickened wall of the cylinder liner is attached to the latter in a leak-proof manner, and which overlaps the exhaust ports and carries ports of its own coinciding with the exhaust ports of the cylinder liner. The thickened wall of each of the cylinder liners being provided with open channels around the exhaust ports such that this area is connected to the cooling water chamber as the open channels are covered by the cooling jacket.